RUSLE2 and the California CGP risk determination
These are two different things, and the difference matters when a reviewer asks for one and you hand over the other. Here is what each one is, and which one your project actually needs.
Rapid RUSLE does not run RUSLE2
Rapid RUSLE performs the RUSLE-based sediment risk determination that the California Construction General Permit calls for, and combines it with receiving water risk to produce a project risk level. It does not run the USDA RUSLE2 model. If your project specifically requires a RUSLE2 analysis, that remains a separate piece of work.
A RUSLE2 integration is something we may add later. It is not in the product today.
What RUSLE2 is
RUSLE2 is the USDA's revised soil loss model, distributed as its own software with a large climate, soil, and management database behind it. It models erosion in detail over a management sequence, and it is built for agricultural and conservation planning as much as for construction.
Some projects, agencies, and reviewers call for a full RUSLE2 analysis. Most California construction projects do not. It is a specialized deliverable, not a routine one.
What the CGP risk determination is
The Construction General Permit determines a project's sediment risk from the RUSLE factors, then pairs that with receiving water risk to set the project risk level. The risk level is what drives your monitoring, inspection, and reporting obligations.
This is the determination nearly every California construction project needs, and it is what Rapid RUSLE produces.
How the sediment risk number is built
The soil loss equation multiplies five factors. For the permit risk determination, two of them are pinned.
A = R × K × LS × C × P
A is average annual soil loss in tons per acre per year. With C and P held at 1.0, the determination reduces to R × K × LS.
Rainfall erosivity
The erosive energy of rainfall and runoff over the project period. Rapid RUSLE retrieves it from the EPA rainfall erosivity service for your project dates and location.
Soil erodibility
How readily a soil detaches and washes away, based on texture, organic matter, structure, and permeability. Read from SSURGO soil survey data, area-weighted across your boundary.
Slope length and steepness
Longer and steeper slopes erode more. Computed from USGS elevation data for your disturbance polygon.
Cover managementFixed at 1.0
Held at 1.0. The permit risk determination represents bare, disturbed ground, so no credit is taken for seeding, mulch, or other cover.
Support practiceFixed at 1.0
Held at 1.0. Erosion control practices such as silt fence and fiber rolls are not credited in the risk determination.
The resulting soil loss bands the site into Low, Medium, or High sediment risk. That band, combined with receiving water risk, sets the project risk level.
What Rapid RUSLE does for you
Enter a project address or upload a KMZ boundary. The inputs are gathered from public datasets and the determination is documented for review.
- R factor from the EPA rainfall erosivity service for your project dates
- K factor from SSURGO soil surveys, area-weighted across your boundary
- LS factor from USGS elevation data for your disturbance polygon
- Sediment risk banded Low, Medium, or High in tons per acre per year
- Receiving water risk cross-referenced against impaired water body datasets
- Combined risk level and a PDF formatted for SWPPP appendices
Rapid RUSLE supports workflow and documentation. It does not guarantee compliance or replace the professional judgment of a QSD or QSP.
Run a risk determination on your own project
Two full-featured projects free, so you can check the numbers against work you have already done.
No credit card required.